FWIW actual analysts that specialize in monitoring North Korean nuclear weapons activity say that not only is there no evidence that the entire complex was destroyed, only one of the three portals were destroyed, but that they don't see evidence that NK will abandon testing at the site altogether:
Analysts keeping an eye on North Korea say “substantial damage” to its nuclear test site could force Pyongyang to abandon the underground complex of tunnels where it has conducted most of its test blasts, and move into other areas.
That assessment—published on Tuesday by the watchdog 38 North, part of the U.S.-Korea Institute at Johns Hopkins SAIS—is based on the severity of North Korea’s sixth (and largest) underground test on September 3, post-blast tremors and observable surface disturbances on Mount Mantap.
“If North Korea were to attempt to continue testing under this mountain (such as in the area more to the eastern side), then we would expect to see new tunneling in the future near the North Portal, still under Mt. Mantap,” states the 38 North report by Frank Pabian and Jack Liu.
“A lack of new tunneling in this area would provide evidence that this mountain has been abandoned for future testing,” the report states. “However, complete abandonment of the test site as a whole remains unlikely.”
The 38 North report states: “While these do make for eye-catching headlines, there was little substance in the articles to back them up beyond quoting the speculative fears of ‘civilian experts.’”
Even in the face of “tired mountain syndrome”—alterations to the rock mass due to multiple nuclear detonations—abandonment of Mount Mantap “should not be expected,” the report states.
The tunnels through the north portal may no longer be in usable condition, but two yet-to-be-used tunnel complexes accessible via south and west portals exist at the site. That means Pyongyang would not have to build new tunnels to continue testing.
“For the time being,” the report concludes, “given the presence of additional test portals, we see no reason that the Punggye-ri Nuclear Test Site as a whole has or will be abandoned for future underground nuclear testing.”
All emphasis is mine. I've seen this theory pop up on reddit a lot lately, and while I'd agree that it would be awesome, I've yet to see it backed up with any type of evidence at all. I certainly don't mean this to be an attack on you but even your comment it is filled with speculation without a single link to a source that would provide evidence to back up the idea. I don't think I've ever seen anyone that has pushed this theory mention that the collapse only happened in one of the areas of the test site....the theory always makes it seem like there is only one set of tunnels at that site and that those tunnels were destroyed when in reality that is objectively untrue. Do you have any actual evidence that you can provide that would back up this theory other than just speculation about "leaked information" coming out of North Korea?